Noticing red lines on your skin that appear after scratching and last for several minutes may indicate a skin reaction called dermatographism, a form of physical urticaria where the skin becomes raised and red after minor irritation. This condition is generally harmless but can be uncomfortable.

• Avoid vigorous scratching to reduce irritation.
• Use gentle moisturizers to soothe the skin.
• If itching or redness worsens or spreads, or if you develop other symptoms like swelling or difficulty breathing, seek immediate medical attention.

It would be best to consult a dermatologist to confirm the diagnosis and discuss possible treatments or preventive measures tailored to your skin. If you want, I can explain more about dermatographism and its management.To narrow down potential causes, we will need some more information.Please tell me your age and gender.